1. Field of the Invention
The present invention relates to an exposure mask and a method of manufacturing the same, and a semiconductor device manufacturing method.
2. Description of the Related Art
Demand for miniaturization of the semiconductor device, such as LSI, is continually strengthened. As a result, device pattern, such as contact hole, is required to have a narrower line width than the wave length of the exposure light used in a exposure equipment. In order to meet such requirement, the illumination that has a high resolution and is suitable for a fine device pattern, e.g., the annular illumination such as the oblique incidence, is employed in the exposure equipment such as the stepper, and the exposure mask to which the optical proximity correction (OPC) is applied is used in the exposure equipment.
Although the annular illumination has a function of enhancing the resolution power as described above, it has such a drawback that an enough depth of focus cannot be gained at the particular pattern pitch. Some technologies for overcoming this problem are known in the art, including the method disclosed in Patent Literature 1.
In Patent Literature 1, an assist feature (opening), called an assist pattern, is formed in the exposure mask as well as the main feature for projecting a device pattern, thereby supplementing the depth of focus that tends to be insufficient at the main feature.
[Patent Literature 1] Patent Application Publication (KOKAI) 2002-122976